Trees suffer from the heatwave

Drought threatens native tree species

Many trees are also suffering from the current heat wave. © Ugurhan / iStock
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Trees under stress: The heat period makes it difficult for many trees native to Germany. Especially sensitive large-leaved species and young urban trees are currently in acute danger, as researchers report. They demand: Because high temperatures and water shortages become more common with climate change in the future, more heat-resistant alternatives must be produced - for example, the Chinese ginkgo.

Yellow leaves, bare branches, falling leaves: If you are currently looking into the treetops, you might think it is already autumn. The current heat period is increasingly troubling the trees in the forest and in the city. They suffer from drought stress, intense sunlight and high ozone levels - with visible consequences.

Young plants especially endangered

Scientists led by Andreas Roloff from the Dresden University of Technology have been researching for some time how trees handle such extreme weather conditions. In the heat seasons 2003 and 2015, it was shown that mainly large-leaved trees such as sycamore maple and summer bark as well as younger plants dried up. Because unlike older trees, they could not reach the declining groundwater with their not fully developed roots.

The foliage already discolored in places: Drought stress in trees © Andreas Roloff

Especially for young urban trees, the situation is therefore critical in long periods of drought. Roloff reports that groundwater is often lowered in built-up areas and is usually below 2 to 3 meters in depth. In addition, areas in the city are often sealed and compacted. All of this makes it even harder for young trees to root and access the precious wet soil.

Extreme location downtown

What is currently observed in many places could become a common sight in the future. With climate change, the situation will continue to worsen for many native species - extreme temperatures and drought may become the norm. For this reason, researchers are now looking for trees that can handle such conditions better. display

"We have been pointing out for ten years that, in addition to winter cottages, heat and dry hazards must rank first and second in the choice of planting, " says Roloff. He predicts that if the cities do not want to become treeless, indigenous tree species will play an increasingly minor role in the next 100 years in extreme locations, for example in inner-city areas.

Ginkgo as an alternative?

But what alternatives are there? Looking for heat-resistant tree species, Roloff and his colleagues have been focusing on Chinese species for more than ten years. For in cities like Beijing, there is already an expected climate for Germany with a fast spring start and long, hot summers.

According to the researchers, under these conditions, for example, the ginkgo is growing well on urban roads. Accordingly, it could better withstand climate change in our latitudes and in the future replace native species in our cities.

(Technical University Dresden, 07.08.2018 - DAL)